Filter leaf

ABSTRACT

A filter segment for a disc filter, having louvered openings providing slotlike drainage passages through its sidewalls and a drainage duct between such sidewalls communicating with the drainage passages to receive filtrate therefrom.

United States Patent [56] References Cited UNITED STATES PATENTS [72]lnventors GillesG.Vallee;

Phillip J. Mills, both of Sherbrooke,

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PATENTED UCT 5 I971 sum 1 0F 2 I a r 2 Ddbdi INVENTORS MILLS ATTORNEYFIG. PHILLIP .1.

GILLES 6. VALLEE 2 BY}? PATENTEDUET Si n 3610.419

sum 2 OF 2 INVENTORS PHILLIP J. MILLS GILLES 6. VALLEE ATTORNEY FILTERLEAF BACKGROUND OF THE INVENTION The present invention relates tofiltering apparatus and more particularly to disc filters of the typeemployed for filtering a slurry such as, for example, pulp stock for themanufacture of paper.

Conventionally, the filter segments which form the filter discs of afilter of this type frequently are provided with drainage openings orpassages extending through the thickness of the segment sidewalls intocommunication with drainage duct means between the sidewalls. The totalflow area of these drainage passages is a determinant of the percentageof liquid or filtrate removed from the stock during the filteringprocess; and such total flow area should be normally as great aspossible to permit maximum draining of liquid from the stock.

In conventional filter segments such passages generally have been in theform of either relatively small cross section openings which communicatewith shallow elongated grooves in the outer face of their respectivesidewall or elongated openings which are constructedthrough thesidewalls in a manner whereby their provision inherently substantiallyreduces the strength of the sidewalls. The formation of the passages inthe configuration of such conventional small cross section openings isbelieved to inherently undesirably limit the attainable total flow areaof the passages. The provision of the passages in the configuration ofsuch conventional elongated openings is, of course, subject to thedeficiency that, as they inherently substantially reduce the sidewallstrength, their total flow area must be maintained at a relatively lowlevel wherein the ratio of such area to the provided sidewall area issufficiently low as to not unduly weaken the sidewalls. Hence, it isbelieved that the construction of the passages in the form of theseconventional elongated openings also undesirably limits the attainabletotal flow area of the passages.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a new and improved filter segment which is particularlyconstructed and arranged such that the drainage passages are formed ofmaximum total flow area with only a minimal reduction in the strength ofthe segment.

Another object of the invention is to provide a new and improved filtersegment of the type set forth which is particularly constructed andarranged whereby filtrate flowing through the drainage passages isdirected towards the base of the segment.

These objects are attained by the provision of a filter segment which,generally considered, may comprise a pair of sidewalls oppositelydisposed in spaced relationship to include remote side faces andadjacent side faces having drainage duct means therebetween, suchsidewalls each including a plurality of louvered openings providingdrainage passages through their thickness in communication with thedrainage duct means for draining filtrate thereto.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings:

FIG. 1 is an elevational side view of a filter segment constructed inaccordance with one embodiment of the invention, shown with a portion ofthe screen wire broken away;

FIG. 2 is an enlarged fragmentary sectional view taken on line 2-2 ofFIG. 1, looking in the direction of the arrows;

FIG. 3 is an enlarged fragmentary sectional view taken on line 3-3 ofFIG. 1 looking in the direction of the arrows; and

FIG. 4 is a fragmentary elevational view illustrating the inner oradjacent side face of one of the sidewalls of the filter segment inconjunction with the reinforcing ribs there adjacent.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly tothe drawings wherein similar reference characters designatecorresponding parts throughout the several views, FIG. 1 illustrates afilter segment or leaf designated generally as 10 which is mounted onthe usual rotatable hub 12 in juxtaposed relationship with other filtersegments adjacent ones of which are indicated fragmentarily in brokenlines. The segment 10, as illustrated, is connected at its outerperiphery to such adjacent segments by clips 14 which internally receivethe segments and are affixed thereto by threaded fasteners 16; and itwill be understood that adjacent segments throughout the filter discincluding the segment 10 will be normally connected in this or anothersuitable manner.

The segment 10 comprises a base designated generally as 18 whichincludes a central boxlike section having walls 20 enclosing adownwardly tapering passage means or duct 42 in communication with oneof the flow channels 24 in the hub 12 for draining filtrate from thesegment 10. The base 18 also includes a pair of mounting flanges 26which project from opposing ones of the walls 20, such mounting flanges26 each being provided with a sleeve 28 containing one of the mountingbolts which detachably connect the segment 10 to the hub 12. The segment10 also comprises a pair of sidewalls 30, 32 each connected at one endto the base 18 and extending longitudinally from the base 18 in opposedspaced relationship such that the sidewalls 30, 32 include inner oradjacent side faces 34 and outer or remote side faces 36. The space 38between the adjacent side faces 34 throughout the lengths and breadthsof the sidewalls 30, 32 serves as a drainage duct or drainage duct meansand communicates with the passage means 22 in the base 18 for drainingfiltrate thereto. The space 38 contains a plurality of suitably arrangedreinforcing or stiffening ribs 40 which provide internal reinforcementfor the segment 10; and such space 38 is closed along its longitudinaledges and its outer peripheral edge by flow barriers 42, 44,respectively, which in the illustrated embodiment of the invention areformed integrally with the sidewalls 30, 32. The flow barriers 42, 44,as illustrated, are connected in overlapping relationship such as bywelding.

In accordance with the present invention louvered openings are formed ineach of the sidewalls 30, 32 to provide drainage passages through thethicknesses of the sidewalls 30, 32 in communication with the space ordrainage duct means 38. More particularly, the sidewalls 30, 32 eachinclude a plurality of elongated offset or recessed portions 46 whichare press formed inwardly into the drainage duct means or space 38whereby the recessed portions 46 each bound an elongated recess 48 inthe remote face 36 of their respective sidewall 30 or 32. The recessedportions 46 are each formed to longitudinally extend laterally ortransversely to the longitudinal axis of their respective sidewall 30 or32; and, as illustrated, each of the sidewalls 30, 32 is provided withfour columns of recessed portions 46, which columns each extend fromadjacent the base 18 and include recessed portions 46 progressivelyincreasing in length as the columns extend from such base 18. Therecessed portions 46 each are formed with their side 50 (i.e., theirside most adjacent to the base 18) spaced inwardly in the space 38 fromthe there adjacent nonrecessed portion 52 of their sidewall 30 or 32;and the elongated or slotlike spaces 54 between the outer faces of suchends 50 and the inner faces of such adjacent nonrecessed portions 52serve as the drainage passages through the sidewalls 30, 32. Therecessed portions 46 are, hence, in effect louvers and are particularlyconstructed to each slope or slant downwardly towards their respectiveslotlike space 54 for facilitating filtrate flow therethrough to thedrainage duct means or space 38. This construction, as will be seen,forms the drainage passages through the sidewalls 30, 32 in a mannerwhereby filtrate flow therethrough is primarily in a directionlongitudinally of the segment 10 and towards the base 18, rather than ina direction essentially crosswise of the segment 10 as would be the casein the event that the drainage passages were in the conventional mannermerely openings punched or molded transversely through the sidewalls 30,32.

The usual or conventional filter screen 56 is wrapped around thesidewalls 30, 32 and supported by the nonrecessed portions 52 andoverlapping flow barriers 42, 44 thereof, whereby the screen 56 overliesthe drainage passages and permits only filtrate to flow thereto.

From the preceding description it will be seen that filtrate flowingthrough the screen 56 passes into the recesses 48 from whence it isdirected by the recessed portions 46 to the drainage passages or spaces54 and into the drainage duct means or space 38. The filtrate, thussupplied to the drainage duct means 38, flows into the passage means orduct 22 in the base 18 from whence it is discharged from the segment toone of the flow channels 24 in the hub 12.

The preferred method for making the filter segment 10 will now bedescribed. In the practice of this method, there are first provided apair of flat or sheet, stainless steel plate ele ments which eachcorrespond in dimensions and shape to the overall dimensions and shapeof one of the sidewalls 30, 32 and its integral flow barriers 42, 44.These plate elements are individually die formed in a press whereby theaforedescribed louvered openings are formed in their portions which willform the sidewalls 30, 32 and the peripheral edges of the plate elementsare bent to form the flow barriers 42, 44. The louvered openings andbent edges may be formed in a single pressing operation or alternativelymay be formed in two or more separate operations.

Then, the reinforcing ribs 40 are affixed to one of the louvered plateelements such as by welding; and the elements are connected into aunitary structure or assembly wherein their louvered portions form thespaced sidewalls 30, 32 by welding or otherwise affixing theircomplementary bent edges in overlapping relationship. The resultantunitary structure is connected at one end to the base 18 by welding orother suitable means whereby the base 18 is rigidly affixed to thestructure; and the screen 56 is in a conventional manner wrapped aroundthe structure in overlying relationship to the outer faces 36 of thesidewalls 30, 32 and the bent edges or fiow barriers 42, 44.

From the preceding description it will be seen that we have provided anew and improved means for accomplishing all of the objects andadvantages of our invention. It will be understood, however, that,although we have illustrated and hereinbefore specifically describedonly one form of a filter segment embodying the invention, thisembodiment has been given by way of illustration only.

Having thus described our invention, we claim:

1. A filter segment for a disc filter, comprising a pair of sidewallsoppositely disposed in spaced relationship to include adjacent sidefaces and remote side faces, said adjacent side faces having drainageduct means therebetween, said sidewalls each including a plurality ofelongated portions ofi'set from adjacent portions thereof, saidelongated offset portions each bounding an elongated recess in one ofthe side faces of their sidewall, said elongated offset portions beingalong their lengths spaced from there adjacent portions of theirsidewalls to provide elongated drainage passages through the thicknessesof such sidewalls between said elongated offset portions and said thereadjacent portions, and said elongated drainage passages communicatingwith said drainage duct means for draining filtrate thereto.

2. A filter segment according to claim 1, wherein said offset portionseach slope downwardly towards their respective drainage passage forfacilitating filtrate flow therethrough.

3. A filter segment according to claim 1, wherein said elongated offsetportions and said elongated drainage passages longitudinally extendtransversely of said sidewalls, said drainage passages are along thesides of said offset portions most adjacent to a single end of thefilter segment, and said offset portions slope downwardly towards theirrespective drainage passages.

4. A filter segment for a disc filter including a hub, comprising a baseadapted for connection to the hub and including passage means fordischarging filtrate from the filter segment, a pair of sidewallsconnected to said base and extending longitudinally from said base inopposed spaced relationship such that said sidewalls include adjacentside faces and remote side faces, said adjacent side faces havingtherebetween drainage duct means and said drainage duct meanscommunicating with said passage means for draining filtrate thereto,said sidewalls each including a plurality of elongated portions recessedfrom adjacent portions thereof, said elongated recessed portionsextending inwardly in the space between said sidewalls and eachproviding an elongated recess in the remote side face of their sidewall,said elongated recessed portions being along their lengths spaced fromthere adjacent portions of their sidewalls to provide elongated drainagepassages through the thicknesses of said sidewalls between each saidelongated recessed portion and said there adjacent portion and saidelongated drainage passages communicating with said drainage duct meansfor draining filtrate thereto.

5. A filter segment according to claim 4, wherein said recessed portionseach longitudinally extend laterally to the longitudinal axis of theirsidewall, and said recessed portions each slope downwardly towards theirdrainage passage for facilitating filtrate flow therethrough.

6. A filter segment according to claim 5, wherein said drainage passagesare at the sides of said recessed portions most adjacent to said base.

7. A filter segment according to claim 6, wherein said sidewalls eachhave integral flow barriers which extend along the peripheral edges ofthe space between said sidewalls, adjacent flow barriers of saidsidewalls being connected in overlapping relation for closing suchperipheral edges.

8. A filter segment for a disc filter including a hub, comprising a baseadapted for connection to the hub and containing passage means fordischarging filtrate from the filter segment, a pair of sidewallsunitary with said base and extending longitudinally from said base inopposed spaced relationship such that said sidewalls include adjacentside faces and remote side faces, said adjacent side faces havingdrainage duct means therebetween and said drainage duct meanscommunicating with said passage means for draining filtrate thereto,said sidewalls each including a plurality of louvered openings providingdrainage passages through their thicknesses in communication with saiddrainage duct means for draining filtrate thereto, the louvers for saidopenings extending transversely of said sidewalls and projecting fromthe latter inwardly in the therebetween space towards said base tolocate said drainage passages at the sides of said louvers most adjacentto said base, and said louvers sloping downwardly towards theirrespective drainage passages and towards said base to facilitatefiltrate fiow through said drainage passages in a direction towards saidbase.

9. A filter segment according to claim 8, wherein said sidewalls eachhave integral flow barriers which extend along the peripheral edges ofthe therebetween space, adjacent flow barriers of said sidewalls beingconnected for closing such peripheral edges.

1. A filter segment for a disc filter, comprising a pair of sidewallsoppositely disposed in spaced relationship to include adjacent sidefaces and remote side faces, said adjacent side faces having drainageduct means therebetween, said sidewalls each including a plurality ofelongated portions offset from adjacent portions thereof, said elongatedoffset portions each bounding an elongated recess in one of the sidefaces of their sidewall, said elongated offset portions being alongtheir lengths spaced from there adjacent portions of their sidewalls toprovide elongated drainage passages through the thicknesses of suchsidewalls between said elongated offset portions and said there adjacentportions, and said elongated drainage passages communicating with saiddrainage duct means for draining filtrate thereto.
 2. A filter segmentaccording to claim 1, wherein said offset portions each slope downwardlytowards their respective drainage passage for facilitating filtrate flowtherethrough.
 3. A filter segment according to claim 1, wherein saidelongated offset portions and said elongated drainage passageslongitudinally extend transversely of said sidewalls, said drainagepassages are along the sides of said offset portions most adjacent to asingle end of the filter segment, and said offset portions slopedownwardly towards their respective drainage passages.
 4. A filtersegment for a disc filter including a hub, comprising a base adapted forconnection to the hub and including passage means for dischargingfiltrate from the filter segment, a pair of sidewalls connected to saidbase and extending longitudinally from said base in opposed spacedrelationship such that said sidewalls include adjacent side faces andremote side faces, said adjacent side faces having therebetween drainageduct means and said drainage duct means communicating with said passagemeans for draining filtrate thereto, said sidewalls each including aplurality of elongated portions recessed from adjacent portions thereof,said elongated recessed portions extending inwardly in the space betweensaid sidewalls and each providing an elongated recess in the remote sideface of their sidewall, said elongated recessed portions being alongtheir lengths spaced from there adjacent portions of their sidewalls toprovide elongated drainage passages through the thicknesses of saidsidewalls between each said elongated recessed portion and said thereadjacent portion and said elongated drainage passages communicating withsaid drainage duct means for draining filtrate thereto.
 5. A filtersegment according to claim 4, wherein said recessed portions eachlongitudinally extend laterally to the longitudinal axis of theirsidewall, and said recessed portions each slope downwardly towards theirdrainage passage for facilitating filtrate flow therethrough.
 6. Afilter segment according to claim 5, wherein said drainage passages areat the sides of said recessed portions most adjacent to said base.
 7. Afilter segment according to claim 6, wherein said sidewalls each haveintegral flow barriers which extend along the peripheral edges of thespace between said sidewalls, adjacent flow barriers of said sidewallsbeing connected in overlapping relation for closing such peripheraledges.
 8. A filter segment for a disc filter including a hub, comprisinga base adapted for connection to the hub and containing passage meansfor discharging filtrate from the filter segment, a pair of sidewallsunitary with said base and extending longitudinally from said base inopposed spaced relationship such that said sidewalls include adjacentside faces and remote side faces, said adjacent side faces havingdrainage duct means therebetween and said drainage duct meanscommunicating with said passage means for draining filtrate thereto,said sidewalls each including a plurality of louvered openings providingdrainage passages through their thicknesses in communication with saiddrainage duct means for draining filtrate thereto, the louvers for saidopenings extending transversely of said sidewalls and projecting fromthe latter inwardly in the therebetween space towards said base tolocate said drainage passages at the sides of said louvers most adjacentto said base, and said louvers sloping downwardly towards theirrespective drainage passages and towards said base to facilitatefiltrate flow through said drainage passages in a direction towards saidbase.
 9. A filter segment according to claim 8, wherein said sidewallseach have integral flow barriers which extend along the peripheral edgesof the therebetween space, adjacent flow barriers of said sidewallsbeing connected for closing such peripheral edges.